1. Field of the Invention
The present invention relates to a semiconductor device in which a semiconductor module and a separate printed wiring board are interconnected in a simple manner by terminals extending from the semiconductor module.
2. Background Art
It is common for semiconductor modules, such as IGBT (Insulated Gate Bipolar Transistor) modules and IPMs (Intelligent Power Modules), to have externally extending terminals. These terminals are used to electrically connect a semiconductor element or elements contained in the semiconductor module to an external wiring board. Examples of such a wiring board include PCBs (Printed Circuit Boards). The present invention is directed to semiconductor devices of the type in which a semiconductor module and a printed wiring board are interconnected by terminals extending from the semiconductor module.
In such semiconductor devices, the printed wiring board is preferably connected to the externally extending terminals of the semiconductor module with the lowest possible contact resistance. Therefore, it is common to connect the printed wiring board to these terminals by means of screws or solder in order to firmly couple them together.
Prior art includes JP-A-5-275872, JP-A-2002-25720, JP-A-10-189108, JP-A-2002-246770, JP-A-7-211363, JP-A-2002-93480, JP-A-2007-35291, JP-A-6-188045, and JP-A-2002-501291 (PCT).
However, the use of solder is not environmentally friendly and hence should preferably be avoided. Further, it is also preferable to avoid the use of screws when the printed wiring board must be connected to a large number of terminals of the semiconductor module, since in such a case the screw fastening takes considerable labor and time. To circumvent this problem, the printed wiring board may be connected to a reduced number of terminals of the semiconductor module with the addition of springs. This, however, may cause the applied compressive force to be concentrated where the terminals are fastened to the printed wiring board by the screws, or may reduce the overall contact force between the terminals and the printed wiring board, resulting in contact failure. Furthermore, the use of springs means an increased number of connections, which may result in an increase in the contact resistance. Further, fixing the printed wiring board to the terminals by the application of compressive force in the manner as described above results in constant exertion of stress on the board, which is not desirable.
Thus, the use of screws alone for connecting the printed wiring board and the terminals of the semiconductor module is disadvantageous in that the screw fastening takes considerable labor and time and, furthermore, the compressive fastening force is locally exerted on those portions of the board around the screws. The use of solder is disadvantageous in that it is not environmentally friendly. Further, the use of springs may result in reduced contact force and hence increased contact resistance at the connections where the printed wiring board is connected to the terminals of the semiconductor module.